Biofuel-Integrated Routes

Despite the enormous potentials of algal biofuels, their costs of production are still too high to compete with fossil fuels. Over the years, applications of algae have spread across various fields. These include applications in the production of high-value and high-volume products and in bioremediation. Making algal biofuels economically feasible requires the adoption of biorefinery concept which properly integrates all/most of the biofuel production with production of pharmaceuticals, nutraceuticals, and cosmetics. Pigments, vitamins, or essential polyunsaturated fatty acids can first be extracted from microalgae before lipid extraction for biodiesel followed by fermentation of defatted biomass for bioethanol. On the other hand, agar, alginate, or carrageenan may be extracted from macroalgae before lipid extraction and the fermentation of lipid-free biomass to bioethanol. To ensure zero waste, spent algal biomass (SAB) can further be fermented or digested anaerobically to produce bio-butanol, dihydroxyacetone, or biogas. Alternatively, SAB may undergo pyrolysis or hydrothermal liquefaction to generate bio-oil, biodiesel, syngas, and biochar. Bioelectricity and algal biomass production may be integrated into wastewater phycoremediation in addition to flue gas sequestration which drastically reduces carbon footprints and addresses the problems of environmental pollution. This chapter holistically presents various integrated routes with respect to economic feasibility of algal biofuels.